The James Webb Space Telescope of NASA, ESA and CSA has enabled another long-sought scientific breakthrough, this time for scientists studying the solar system and investigating the origins of the water that made life on Earth possible.

Using Webb's NIRSpec (Near-Infrared Spectrograph) instrument, astronomers have confirmed for the first time the presence of water, in the form of vapor, around a comet in the main asteroid belt — located between the orbits of Mars and Jupiter — demonstrating that water from the early solar system can be stored as ice in that region.

NASA/ESA/CSA

Comet 238P/Read photographed by James Webb telescope

However, the successful detection of water brings a new conundrum: unlike other comets, comet 238P/Read has no carbon dioxide, which typically makes up about 10 percent of the volatile material of these objects and can be easily vaporized by the Sun's heat.

The scientific team has put forward two possible explanations for this mystery. One possibility is that Comet Read had carbon dioxide when it formed, but lost it due to warm temperatures. "Being in the asteroid belt for a long time could do that: carbon dioxide vaporizes more easily than water ice and could leak out for billions of years," explained astronomer Michael Kelley of the University of Maryland and lead author of the study. Alternatively, he said, Comet Read may have formed in a particularly hot pocket in the solar system, where no carbon dioxide was available.

Webb Telescope

Emission spectrum of comet Read

Scientists have long speculated that water ice could be preserved in the hottest asteroid belt, within Jupiter's orbit, but the definitive evidence was elusive — to this day. "We've seen objects in the main belt with all the characteristics of comets in the past, but only with this precise Webb spectral data can we say that it's definitely the water ice that's creating that effect," Kelley said.

"Our water-filled world, teeming with life and unique in the universe as far as we know, is something mysterious — we're not sure how all this water got here," said Stefanie Milam, Webb Deputy Project Scientist for Planetary Science and co-author of the study published in the journal Nature reporting the discovery.

"Understanding the history of water distribution in the Solar System will help us understand other planetary systems and whether they might be on track to host an Earth-like planet," he added.